1. Field of the Invention
The present invention relates to a vehicle state estimating device, a vehicle state estimating method, and a vehicle control device.
2. Description of the Related Art
A detection device for detecting a roll of a vehicle based on a wheel speed is conventionally known. For example, Japanese Patent Application Laid-open No. 5-319051 discloses a roll detection device for detecting a rotation movement about a front-back axis of a vehicle, the roll detection device including first and second wheel speed detection units that detect wheel speeds on the left and right of the vehicle, respectively; first and second wheel speed fluctuation amount extracting units for obtaining a fluctuation amount of the wheel speed in a sprung resonance frequency region for each of the left and right wheels based on detected left and right wheel speeds; and a roll computing unit for computing a magnitude of the rotation movement about the front-back axis of the vehicle based on a reverse phase component of the obtained fluctuation amount for the left and right wheels.
The fluctuation amount of the wheel speed is subjected to the influence of not only the behavior of a sprung portion but also the behavior of an unsprung portion. Thus, for example, the difference in the wheel speeds of the left and right wheels may not necessarily indicate the roll as is. Furthermore, the fluctuation amount of the wheel speed contains a component generated by the sprung behavior caused by an operation input. If the vehicle state is estimated from the fluctuation amount of the wheel speed containing such component, an accurate estimation may not be carried out. Thus, improvements still can be made in enhancing the accuracy of when estimating the state amount of the vehicle from the wheel speed.